Electrical stimulation of nerves and surrounding tissue is used to treat a variety of conditions. For example, electrical stimulation can be used to restore partial function to limbs or organs following traumatic injury. Electrical stimulation can also be used to reduce pain. Specifically, electrical stimulation can be used to treat disorders associated with the gastrointestinal (GI) system, such as, obesity and gastroesophageal reflux disease (GERD).
Gastro-esophageal reflux disease (GERD) is a common health problem and is expensive to manage in both primary and secondary care settings. This condition results from exposure of esophageal mucosa to gastric acid and bile as the gastro-duodenal content refluxes from the stomach into the esophagus. The acid and bile damages the esophageal mucosa resulting in heartburn, ulcers, bleeding, and scarring, and long term complications such as Barrett's esophagus (pre-cancerous esophageal lining) and adeno-cancer of the esophagus. Patients with GERD may only experience symptoms during the day, referred to as diurnal GERD, and may not experience any GERD symptoms at night, referred to as nocturnal GERD. Diurnal or daytime or upright GERD has been associated with tLESR, and may be diagnosed where a patient has symptoms of heartburn, regurgitation or both.
The severity of GERD increases progressively from postprandial to upright, to supine, to bipositional reflux. A structural defect as reflected by decreased LES pressure and length is also significantly less common with postprandial and upright reflux. The improved esophageal sensation associated with improved saliva production that neutralizes the refluxed acid and increased clearance of the refluxate aided by gravity results in lesser esophageal damage.
Lifestyle advice and antacid therapy are advocated as first line treatments for the disease. However, since most patients with moderate to severe cases of GERD do not respond adequately to these first-line measures and need further treatment, other alternatives, including pharmacological, endoscopic, and surgical treatments are employed.
The most commonly employed pharmacological treatment is daily use of H2 receptor antagonists (H2RAs) or proton-pump inhibitors (PPIs) for acid suppression. Since gastro-esophageal reflux disease usually relapses once drug therapy is discontinued, most patients with the disease, therefore, need long-term drug therapy. However, daily use of PPIs or H2RAs is not universally effective in the relief of GERD symptoms or as maintenance therapy. Additionally, not all patients are comfortable with the concept of having to take daily or intermittent medication for the rest of their lives and many are interested in nonpharmacological options for managing their reflux disease.
Several endoscopic procedures for the treatment of GERD have been tried. These procedures can be divided into three approaches: endoscopic suturing, wherein stitches are inserted in the gastric cardia to plicate and strengthen the lower esophageal sphincter; endoscopic application of energy to the lower esophagus; and, injection of bulking agents into the muscle layer of the distal esophagus. These procedures, however, are not without their risks, besides being technically demanding and involving a long procedure time. As a result, these procedures have largely been discontinued.
Open surgical or laparoscopic fundoplication is also used to correct the cause of the disease. However, surgical procedures are associated with significant morbidity and small but not insignificant mortality rates. Moreover, long-term follow-up with patients treated by surgery suggests that many patients continue to need acid suppressive medication. There is also no convincing evidence that fundoplication reduces the risk of esophageal adenocarcinoma in the long term.
Electrical stimulation is one methodology aimed at treating GERD. Electrical stimulation employs an implantable, pacemaker-like device to deliver low-level electrical stimulation to portions of the esophagus and/or stomach. For example, in U.S. Pat. No. 6,901,295, assigned to the applicant of the current invention, “A method and apparatus for electrical stimulation of the lower esophageal sphincter (LES) is provided. Electrode sets are placed in the esophagus in an arrangement that induce contractions of the LES by electrical stimulation of the surrounding tissue and nerves. The electrical stimulus is applied by a pulse generator for periods of varying duration and varying frequency so as to produce the desired contractions. The treatment may be short-term or may continue throughout the life of the patient in order to achieve the desired therapeutic effect. The stimulating electrode sets can be used either alone or in conjunction with electrodes that sense esophageal peristalsis. The electrode sets can be placed endoscopically, surgically or radiologically.” The referenced invention relies on sensing certain physiological changes in the esophagus, such as changes in esophageal pH, to detect acid reflux. Once a change in esophageal pH is recognized, the system generates an electrical stimulation in an attempt to instantaneously close the LES and abort the episode of acid reflux. U.S. Pat. No. 6,901,295 is hereby incorporated by reference in its entirety.
While current electrical stimulation systems are effective in treating GERD, they do not address all of the anatomical factors involved in the cause of the disease. Particularly, patients suffering from GERD often exhibit a shortened LES high pressure zone. The LES high pressure zone is a segment of the LES in which the pressure is higher than the pressure in the immediately proximal and distal portions of the esophagus. The higher pressure in this zone helps to keep stomach contents from refluxing. A shortened zone presents less resistance to refluxing gastric acid. Lengthening the LES high pressure zone would create a longer barrier to refluxing stomach contents. Therefore, what is needed is an electrical stimulation system which acts to increase the length of the LES high pressure zone, thereby reducing the frequency and severity of GERD.